Ar Gas Flow Rate Research Articles

Precise control over physical characteristics of Carbon Nanotubes by differential variation of Argon flow rate during Chemical Vapor Deposition processing: A systematic study on growth kinetics

In this paper, we report a systematic work on growth analysis of carbon nanotubes (CNTs) using thermal CVD method where fine tuning of CNTs׳ physical characteristics, i.e. length(height of carpet), diameter, number of walls and orientation have been greatly achieved by simply varying the Argon(Ar) gas flow rate in the Ar and Acetylene gas mixture. Ar flow rate was varied from 0 to 100sccm with 20sccm interval and the growth evolution was monitored by FESEM, HRTEM, and Raman spectrometer. A gradual change was observed in the reduction of diameter, increase in height, decrease in defect density, and change in orientation from horizontal to vertical of the CNTs grown over the prescribed flow rate range. Growth mechanism is discussed at every step of Ar flow rate in consideration of the analysis done on the image from electron microscopes and Raman spectra.

Inactivation of Escherichia coli using atmospheric-pressure plasma jet

An atmospheric-pressure argon (Ar) plasma jet was applied to the inactivation of Escherichia coli. The Ar plasma jet was generated at a frequency of 10 kHz, an applied voltage of 10 kV, and an Ar gas flow rate of 10 L/min at atmospheric pressure. E. coli cells seeded on an agar medium in a Petri dish were inactivated by Ar plasma jet irradiation for 1 s. Scanning electron microscopy (SEM) revealed that E. coli cells were killed because their cell wall and membrane were disrupted. To determine the causes of the disruption of the cell wall and membrane of E. coli, we performed the following experiments: the measurement of the surface temperature of an agar medium using a thermograph, the analysis of an emission spectrum of a plasma jet obtained using a multichannel spectrometer, and the determination of the distribution of the concentration of hydrogen peroxide (H2O2) generated on an agar medium by plasma jet irradiation using semiquantitative test strips. Moreover, H2O2 solutions of different concentrations were dropped onto an agar medium seeded with E. coli cells to examine the contribution of H2O2 to the death of E. coli. The results of these experiments showed that the cell wall and membrane of E. coli were disrupted by electrons in the plasma jet, as well as by electroneutral excited nitrogen molecules (N2) and hydroxyl (OH) radicals in the periphery of the plasma jet.

Graphene treatment using a very low energy Ar+ ion beam for residue removal.

The effect of Ar+ ion energy on the removal of the polymethyl methacrylate (PMMA) residue remaining on the chemical vapor deposited (CVD) graphene surface without damaging the graphene surface was investigated. Stable and low energy Ar+ ion beams having a mono-energetic energy distribution with a peak energy of 7.5 eV or 11.5 eV could be formed by using a two-grid magnetically enhanced ICP ion gun with and without the application of 25 Gauss axial magnetic field, respectively, while controlling the Ar gas flow rate. When the CVD graphene treatment was performed with the Ar+ ions having the ion energy peak at 7.5 eV (with the magnetic field) and 11.5 eV (without the magnetic field), the blue shift of Raman G peak from p-type doped to intrinsic graphene indicating the removal of residue on the graphene surface could be observed for both conditions, however, the graphene treated at 11.5 eV (without the magnetic field) showed the increase of the defect while that treated at 7.5 eV (with the magnetic field) showed no significant change of the defect. It is believed that, for the treatment of CVD graphene, possibly due to the low binding energy area such as grain boundaries and domains in the CVD graphene, low energy ions with less than the energy of 10 eV is required not to damage the graphene surface, and a magnetically enhanced ICP ion gun which can provide stable and low energy Ar+ ions with a mono-energetic ion energy distribution with a peak of 7.5 eV can be applicable to the residue removal on the graphene surface.

Van der Waals epitaxial growth of topological insulator Bi2−xSbxTe3−ySey ultrathin nanoplate on electrically insulating fluorophlogopite mica

We report the growth of high quality Bi2−xSbxTe3−ySey ultrathin nanoplates (BSTS-NPs) on an electrically insulating fluorophlogopite mica substrate using a catalyst-free vapor solid method. Under an optimized pressure and suitable Ar gas flow rate, we control the thickness, the size, and the composition of the BSTS-NPs. Raman spectra showing systematic change indicate that the thicknesses and compositions of the BSTS-NPs are indeed accurately controlled. Electrical transport demonstrates a robust Dirac cone carrier transport in the BSTS-NPs. Since the BSTS-NPs provide superior dominant surface transport of the tunable Dirac cone surface states with negligible contribution of the conduction of the bulk states, the BSTS-NPs provide an ideal platform to explore intrinsic physical phenomena as well as technological applications of 3-dimensional topological insulators in the future.

High Selectivity in Dry Etching of Silicon Nitride over Si Using a Novel Hydrofluorocarbon Etch Gas in a Microwave Excited Plasma for FinFET

The SiNx gate spacer formation is one of the key processes in the miniaturized MISFETs, because the thickness of the gate spacer and the Si recess after the gate spacer formation etching have large impacts on the electrical properties of MISFETs [1,2]. High selectivity of SiNx over Si is strongly required in MISFETs such as extremely thin silicon on insulator (ETSOI) device and 3 dimensional (3D) MOSFET for the reduction of the series resistance [1,2]. Various etching gases were evaluated in order to obtain high selectivity of SiNx over Si[3-6]. It is considered that a plasma source and etching gases are important in order to obtain high selectivity dry etching of SiNxover Si. We consider that the plasma source with low electron temperature is advantageous in the improvement of selectivity, because it prevents excessive dissociation of the etching gas. The difference of the chemical structures of etching gas with the plasma source can make a difference of the selectivity. In this work, we utilized the microwave excited plasma source that has the characteristic of low electron temperature and a novel gas (SSY525 made by ZEON) [7].Figure 1 shows the selectivity of SiNx to poly Si as a function of O2 flow rate. The flow rate of SSY525 and CH3F are 8 sccm and 10 sccm, respectively. The microwave power, the RF power of bottom electrode and the Ar gas flow rate were 1000 W, 60 W and 200 sccm, respectively. SiNx films were deposited by PECVD and LPCVD. Si/N ratio and density of SiNx by PECVD was lower than those by LPCVD [8]. In the case of SSY525, a higher selectivity of SiNx by PECVD and LPCVD to poly Si was obtained with O2 flow rate from 0 to 50 sccm to CH3F. Low etch rate of poly Si less than 0.3 nm/min and high selectivity of SiNx to Si over 50 were obtained with O2 flow rate of 0 sccm and more than 30 sccm. Figure 2 shows the analysis of poly Si surface by XPS after dry etching using SSY525. A high intensity of C 1s was obtained with O2 flow rate of 0 sccm. It is considered that high selectivity of SiNx to poly Si was obtained due to carbon deposition on poly Si surface. The intensity of C 1s decreases and the intensity of O 1s increases as the O2 flow rate increases. It is considered that High selectivity of SiNx to poly Si is obtained with O2 flow rate more than 30 sccm due to an oxidation of poly Si surface. Figure 3 (a) shows the schematic of 3D-MISFET structure. Figure 3 (b)-(d) show the cross-section SEM images from A to B in Fig. 3 (a) with various SSY525 flow rate. A 40 nm-thick SiNx was overetched at (b) 8 sccm, (c) 12 sccm and (d) 15 sccm. Si near the SiNx sidewall was etched with SSY525 of 8 sccm. It was not etched with SSY525 more than 12 sccm. About 5 nm-thick film containing carbon was deposited on the Si surface with 15 sccm. In the cases of (c) and (d), high selectivity of SiNx over Si was obtained. It is confirmed that SSY525 is effective in order to form the SiNxgate spacer in the miniaturized MISFET.

Effects of gas flow rate on structural features of ZnO nanowire arrays fabricated on silicon substrate

Arrays of single-crystal zinc oxide (ZnO) nanowires have been synthesized on silicon substrates by vapor–liquid–solid growth techniques. The effect of growth conditions including the substrate temperature and Ar gas flow rate on the growth properties of ZnO nanowire arrays were studied. Structural and optical characteristics were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) spectroscopy. The XRD measurements showed that the single-crystal nanowires exhibited growth in the (002) direction. SEM images of the ZnO nanowire arrays grown at various Ar gas flow rates indicated that the alignment and structural features of the ZnO nanowires were affected by the gas flow rate. The PL of the ZnO nanowire arrays exhibited strong UV emission at 380 nm and weak green emission at approximately 510 nm. A blue shift and broadening of the UV emission were observed with increasing Ar gas flow rate.

Investigation on the bonding behavior of the interface within the supersonic plasma sprayed coating system based on the fractal theory

In order to investigate the relationship between the interfacial morphology of the coating system and its adhesion strength, the supersonic plasma spraying equipment is employed to fabricate Fe-based alloy coating. The (Ni, Al) coating is prepared as the undercoating with different flow of Ar gas, aiming at obtaining various rough morphologies. Interfacial morphologies of the coating system are quantificationally characterized by fractal dimension(FD). The pull-off method is used to test the adhesion strength. Result shows that the adhesion strength is obviously improved by fabricating an undercoating, and the FD of the interfacial morphology decreases with the increase of the flow rate of Ar gas, while the adhesion strength will be raised at the first beginning and then decreased to a certain value.

Postdeposition Annealing Effect on Cu2ZnSnS4Thin Films Grown at Different Substrate Temperature

Cu2ZnSnS4(CZTS) thin films were deposited on top of Molybdenum (Mo) coated soda lime glass (SLG) substrates using a single target rf magnetron sputtering technique. The sputtering parameters such as base pressure, working pressure, rf power, argon (Ar) gas flow rate, and deposition time were kept consistent throughout the experiment. The effect of different substrate temperatures, for example, room temperature (RT), 300°C, 350°C, 370°C, 400°C, and 450°C, was analyzed by studying their structural, electrical, and optical properties. As-sputtered films were then annealed at 460°C. X-ray diffraction (XRD) measurement revealed the structure to be kesterite with peak of (112) plane in both annealed and as-sputtered CZTS thin films. The crystallinity of the films improved with the increasing substrate temperature until 370°C. Secondary phases of MoS2,CuxMoSx,CuxSnSx,CuxS, and Cu6MoSnS8(hemusite) were also observed in the annealed CZTS films. Scanning electron microscopy (SEM) shows crystallite size of deposited CZTS thin film to be proportionally related to deposition temperature. The highest surface roughness of 67.318 nm is observed by atomic force microscopy (AFM). The conductivity type of the films was found to be p-type by Hall effect measurement system.

Preparation and characterization of molybdenum disilicide coating on molybdenum substrate by air plasma spraying

MoSi2 oxidation protective coatings on molybdenum substrate were prepared by air plasma spraying technique (APS). Microstructure, phase composition, porosity, microhardness and bonding strength of the coatings were investigated and determined. Oxidation behavior of the coating at high temperature was also examined. Results show that composition of the coatings is constituted with MoSi2 and Mo5Si3, the surface morphology is described as flattened lamellar features, insufficiently flattened protuberance with some degree of surface roughness, a certain quantity of spherical particles, microcracks and pores. Testing results reveal that microhardness and bonding strength of the coatings increase, and porosity decreases with increasing power or decreasing Ar gas flow rate. Moreover, with decreasing the porosity, the microhardness of the coatings increases. The bonding strength of the coatings also increases with increasing spray distance. The MoSi2 coated Mo substrate exhibited a good oxidation resistance at 1200°C.

AZO 투명전극의 결정성과 광학적 특성

The optical properties of AZO thin films prepared by the RF mangnetron sputtering system was studied to research the dependance of chemical properties of substrate. The substrate was the SiOC film deposited by Inductively coupled plasma chemical vapor deposition with various gas flow rate of and Ar (DMDMOS). In accordance with the increase of Ar gas flow rates, the Si-O bond in the SiOC film increased and then progressed the amorphism. The roughness of AZO grown on SiOC film with high degree of amorphism decreased and then improved the flatness of surfaces. Moreover, the ultra violet emission with high intensity was spontaneously induced in the AZO film growed on SiOC film with high degree of amorphism.

Numerical study of the effect of gas flow in low pressure inductively coupled Ar/N2 plasmas

Abstract The effect of gas flow in low pressure inductively coupled Ar/N2 plasmas operating at the rf frequency of 13.56 MHz and the total gas pressure of 20 mTorr is studied at the gas flows of 5–700 sccm by coupling the plasma simulation with the calculation of flow dynamics. The gas temperature is 300 K and input power is 300 W. The Ar fractions are varied from 0% to 95%. The species taken into account include electrons, Ar atoms and their excited levels, N2 molecules and their seven different excited levels, N atoms, and Ar+, N+, N2 +, N4 + ions. 51 chemical reactions are considered. It is found that the electron densities increase and electron temperatures decrease with a rise in gas flow rate for the different Ar fractions. The densities of all the plasma species for the different Ar fractions and gas flow rates are obtained. The collisional power losses in plasma discharges are presented and the effect of gas flow is investigated.

Giant Magnetoresistance in (Ni<sub>60</sub>Co<sub>30</sub>Fe<sub>10</sub>/Cu) Trilayer Growth by Opposed Target Magnetron Sputtering

The giant magnetoresistance thin film of (Ni60Co30Fe10/Cu) trilayer were grown onto Si (100) substrate by dc-opposed target magnetron sputtering (dc-OTMS) technique. The growth parameters are: temperature of 100 0C, applied voltage of 600 volt, flow rate of Ar gas of 100 sccm, and growth pressure of 5.2 x10-1 Torr. The effects of Cu layer thickness and NiCoFe layer thickness on giant magnetoresistance (GMR) property of (Ni60Co30Fe10/Cu) trilayer were studied. We have found that the giant magnetoresistance (GMR) ratio of the sample was varied depend on the non-magnetic (Cu) layer thickness. The variation of Cu layer thickness presents an oscillatory behavior of GMR ratio. This oscillation reflects the exchange coupling oscillations between ferromagnetic and antiferromagnetic states, which are caused by an oscillation in the sign of the interlayer exchange coupling between ferromagnetic layers. The GMR ratio is change with increasing of NiCoFe layer thickness and presents GMR ratio of 70.0 % at tNiCoFe = 62.5 nm.

High frequency characteristics of FeCoAlO thin films fabricated with asymmetric target at different Ar gas flow rates

FeCoAlO thin films with good soft magnetic properties were fabricated by using RF magnetron sputtering. In order to obtain good high-frequency performance, the in-plane uniaxial anisotropy was tuned by combining the effects of in situ magnetic field and the gradient of Al–O concentration. The composition gradient was controlled by using an asymmetric target and different Ar gas flow rates changing from 5 sccm to 17.5 sccm. It was found that at the range of Ar gas flow rate from 7.5 sccm to 15 sccm, the films showed an excellent high-frequency performance: the resonance frequency was beyond 3.0 GHz and the real permeability μ′ had a high value of ∼200 at low-frequency side. In particular, the film prepared at the Ar gas flow rate of 15 sccm showed a resonance frequency of 4.0 GHz. Large resonance frequency can be attributed to the high in-plane uniaxial anisotropy field which was induced by stress and the external magnetic field. The high values of permeability and resonance frequency enable the FeCoAlO thin films to be one of the important candidates for microwave applications.

플라즈마 처리된 폴리프로필렌 표면 위에 글리시딜메타크릴레이트의 에멀젼 그래프팅

Glycidyl methacrylate (GMA) was used to introduce epoxy groups on the surface of polypropylene (PP) plate, used as a substrate, through plasma-induced graft copolymerization. Emulsion polymerization was applied for graft copolymerization of GMA and was compared with conventional solution polymerization to confirm its effect. Plasma treatment conditions under one atmospheric pressure were fixed as follows; the RF power of 200 W, the treatment time of 30 sec, the Ar gas flow rate of 6 LPM, and the exposure time of treated PP samples in air of 5 min. For graft-copolymerization, GMA concentration, reaction temperature, and reaction time was optimized to maximize the grafting degree of GMA. The maximum grafting degree of GMA was obtained at the condition of 12%-GMA concentration, reaction temperature, and 5 hr-reaction time. Analysis results supported that the emulsion polymerization was more effective than the solution polymerization for grafting more GMAs on the surface of PP plate under the same reaction conditions.

流動下での濡れ性の悪い耐火物からの気泡の生成とAr気泡によるタンディッシュ内での介在物除去

The injection method of Ar gas into the molten steel through porous plug is usually applied to the removing process of the nonmetallic inclusions. It is commonly confirmed by many studies on this method that the availability of the injected Ar gas increases with the decreasing bubble diameter. In this paper, the influence of the pore diameter, flow rate of Ar gas, the wettability between liquid and porous plug and the streaming velocity of liquid on the bubble diameter is experimentally examined and the obtained results are analytically discussed. When Ar gas is injected into the stationary liquid through the wettable porous plug the bubble diameter increases with the increasing pore diameter and flow rate of Ar gas. In case of the wettability is bad the bubble diameter grows up greater and shows almost constant value regardless of the injection conditions. To make this grown bubble fine it is effective to give a stream to the liquid. The experimental results were applied to the manufacturing equipment aiming to make the molten steel clean in tundish. This test showed that the Ar gas bubble by the streaming molten steel has a removing ability of the nonmetallic inclusions in molten steel.

Effect of Process Gases on Fabricating Tapered Through-Silicon vias by Continuous SF6/O2/Ar Plasma Etching

We report on a continuous plasma etching process using SF6/O2/Ar gases for fabricating 100 μm deep tapered through-silicon vias (TSV). The mask diameters of the vias were 20, 30 and 50 μm. The flow rates of the process gases were changed to study their individual effect on the profile angle, via depth, sidewall roughness, and sideways undercut of the tapered vias. Tapered vias having profile angles varying from 70° to 85° and smooth sidewalls were etched by balancing the chemically-assisted isotropic etching of F* radicals, passivation film by O2, and ion-assisted passivation etching. Although, the profile angles of the etched vias were reduced by either increasing the SF6 flow rate or by reducing the O2 flow rate, the effect of SF6 gas was found to be dominant. The flow rates of SF6 and O2 were found to be the important factors which determine the continuous tapering of the vias with smooth via sidewalls. Ar gas flow rate did not significantly affect the tapered silicon vias and the profile angle. After considering the individual effects of each gas, an optimized etching recipe was fixed, which was used to etch 100 μm deep vias having a profile angle of 83°. Conformal layers of insulation and copper seed layers were deposited in the tapered vias. The tapered vias were partially filled by copper electrodeposition and redistribution lines were formed. The electrical resistance of tapered TSVs was measured to be between 3–8 mΩ for the majority of the TSVs, making these TSVs suitable for various MEMS packaging applications.

ZnO:Al Thin Films with Buffer Layers Fabricated via Nitrogen Mediated Crystallization: Effects of N<sub>2</sub>/Ar Gas Flow Rate Ratio

ZnO:Al Thin Films with Buffer Layers Fabricated via Nitrogen Mediated Crystallization: Effects of N<sub>2</sub>/Ar Gas Flow Rate Ratio

A Study on the Effect of Process Parameters on Surface Topography of Al Thin Films on Various Substrates Using AFM

Al thin films were prepared over different substrates at various process conditions using DC sputtering. The surface topography of all prepared films was examined using AFM technique. Very smooth, uniform and dense surface were observed for Al films coated over Glass substrates. The observed particle size was nano scale (20 -70 nm) for Glass substrates. Sputtering power showed immense effect on surface roughness with respective to Ar gas flow rate. Noticeable change on surface with large particles was observed in Copper substrates at various sputtering power and gas flow rate.

Behaviors of Plasma Bullet Propagation and Effects of Gas Flow Rate

An Ar dielectric-barrier-discharge atmospheric-pressure plasma jet (APPJ) driven by a 34-kHz sinusoidal power source is employed to investigate plasma bullet propagation in positive and negative half cycles by using an intensified charge-coupled device camera. The effects of different Ar gas flow rates on plasma bullet behavior are also presented in this paper. It is found that the duration and velocity of bullets in a positive discharge current pulse are significantly shorter and faster than those in a negative discharge current pulse and APPJ seems easier to form the plasma bullet phenomena during the positive discharge current pulse. The differences between positive and negative discharge current pulses can be explained by using the cathode-directed streamer and negative corona theories, respectively. It is considered that, due to the possible turbulence flow, the propagation length of plasma bullets is decreased with the increment of gas flow rates.

The Growth Mechanism of Vertically Aligned ZnO Nanowire Arrays on Non‐epitaxial Si(100) Substrates

AbstractIn this report, we have investigated the Au‐assisted growth of ZnO nanowires at a low temperature (550 °C) using low melting point Zn metal as a source. We supplied various Ar gas flow rate to carry Zn vapor onto Au catalysts coated Si(100) substrates to grow ZnO nanowires. When a high Ar gas flow rate was supplied, a large amount Zn vapor was carried onto the substrate and reacted with O2 to form a ZnO buffer layer covering the surface of the Au catalysts. This ZnO buffer layer has a highly c‐axis preferential orientation, which helps form vertically aligned ZnO nanowire arrays. In this condition, no Au catalysts appeared on the tips of the ZnO nanowires. When low Ar gas flow rate was supplied, Zn vapor is too low to form ZnO buffer layer on the surface of Au catalysts. From TEM analysis, we can observe that Au catalysts remain solid during growth. The detail growth mechanism of ZnO nanowires with various carrier flow rates was studied by field‐emission electron microscopy (FE‐SEM), transmission electron microscopy (TEM) and X‐ray diffraction (XRD).